Labcorp Plasma Detect 
MRD Solutions

Molecular Residual Disease (MRD) refers to the subclinical presence of microscopic cancer that persists after surgery or definitive treatment. These traces are undetectable by physical exam or standard imaging techniques but indicate a high risk of recurrence. MRD testing uses advanced molecular diagnostic techniques to detect these traces of cancer cells with greater sensitivity than conventional methods such as radiographic imaging. 

MRD testing measures tumor-derived molecular signals in blood, primarily ctDNA variants (single nucleotide variants, indels, structural signals) that indicate the presence of residual cancer cells below the detection threshold of conventional imaging approaches.  Labcorp Plasma Detect MRD assays also quantifies ctDNA burden to monitor changes over time. 

Two main clinical approaches exist: 

1. Tumor-informed workflow: The patient’s tumor is sequenced to create a personalized ctDNA signature, which is then tracked in serial blood samples. This method offers high sensitivity because it monitors patient or tumor-specific variants. All Labcorp MRD solutions are based on tumor-informed approach
2. Tumor-naïve (plasma-only) workflow: Predefined gene panels are evaluated in the plasma without prior tumor sequencing. This approach offers lower sensitivity, however, it eliminates the need for tumor sampling

Both approaches involve sample (blood +/- tumor tissue) collection, sequencing and bioinformatic analysis for MRD assessment. 
 

A baseline timepoint refers to the first ctDNA timepoint for a patient, it can be before or after curative intent therapy (such as surgery and/or adjuvant chemotherapy). It often overlaps with landmark timepoint as the first ctDNA sample is taken within the predefined time frame after curative intent therapy.

A longitudinal timepoint refers to any subsequent timepoint after the initial (baseline) MRD assessment, used to monitor ctDNA dynamics during surveillance.

There’s no one universal schedule; frequency and timing depend on clinical indication and context. Common clinical patterns include:

• A baseline draw after definitive treatment (i.e., surgery +/- adjuvant chemotherapy) for risk stratification and adaptive treatment decisions
• Monitoring draws every 3-6 months or per physician/clinical trial protocol to monitor treatment response or detect disease recurrence
   

MRD testing is not universally applied across all solid tumor types. Current clinical use focuses on tumor types and settings with the most robust evidence for prognostic or predictive value (e.g., bladder and colorectal cancers). Broader clinical utility depends on tumor biology, clinical context and available supporting data. Ultimately, use is guided by clinical indications and the discretion of the treating oncologist.

ctDNA positive refers to the presence of ctDNA-associated variants in the blood after curative-intent therapy. Clinically this suggests a higher risk of disease recurrence, used to risk stratify and enable adaptive treatment decisions (i.e., escalation or de-escalation of adjuvant therapy, surveillance intensity or clinical trial enrollment).  Multiple studies demonstrated that ctDNA positivity post-surgery is strongly prognostic of disease relapse. 

ctDNA negative refers to the absence of ctDNA-associated variants in the blood at the tested timepoint (baseline or monitoring). ctDNA negative result indicates lower disease recurrence risk. However, false negatives can occur (e.g., low-shedding tumors, timing of testing relative to treatment, technical limits), so results should be interpreted alongside clinicopathologic risk factors.